The call for a chemically-based medicine by Paracelsus in the early sixteenth century led to a violent confrontation with the Galenic medical establishment. In the course of the seventeenth century the more mystical aspects of the Paracelsian world view were discarded while the practical chemically-prepared medicines became so popular that chemistry itself was accepted as part of medical training in the universities of Europe. Along with a respected chemical pharmacy came a renewed interest in chemical explanations of physiological processes. The work of van Helmont, Willis and de la Boe Sylvius presented a new iatrochemistry at the same time that the mechanical philosophy became predominant in the physical sciences. Physicians who sought a reformed medicine based on physics, iatrophysicists such as Baglivi and Borelli, sharply opposed those who sought a medicine founded on chemistry. The earlier chemical cosmology based on the analogies of the macrocosm and the microcosm may have been largely forgotten by the closing decades of the seventeenth century, but the chemical medicine of the followers of van Helmont continued to be hotly debated throughout the early decades of the new century. The sharp attacks on iatrochemistry--particularly as it was developed in the acid-base theory--by Boerhaav-e and Stahl promoted in the first case a severely mechanical interpretation of the human body, and in the second, an animistic medicine that was to become dominant at Montpellier. A series of specific debates in the early eighteenth century such as the attack on the iatrochemist Vieussens by the iatrophysicist Hecquet contribute to our understanding of this confrontation. These chemical and medical debates of the late seventeenth and the early eighteenth centuries have not been adequately studied by historians. They deserve careful examination not only for their bearing on the development of medicine in that period, but also for a better understanding of the interaction of medicine and chemistry in the period of the Scientific Revolution. This is the goal of the proposed research, a book length study of this debate and its consequences for the medical scene of the eighteenth century.